1. Field of the Invention
The present invention relates to a lubricant applying system for a rolling bearing, in particular, an apparatus for applying a lubricant to the interior of a rolling bearing, and an apparatus for inspecting a lubricant applied condition of a rolling bearing adapted to inspect whether or not a lubricant is applied to the interior of the rolling bearing.
2. Description of the Related Art
FIG. 15 shows the construction of a rolling bearing. In the figure, reference numeral 700 denotes a rolling bearing, which is constituted by an outer race 701, an inner race 702 and a crown-shaped retainer 704 provided between the races for retaining a plurality of ball-like rolling elements 703.
Known as a conventional method for applying a lubricant to the interior of thus rolling bearing 700 is describes an oil plating method for slightly applying a lubricant on a bearing raceway surface (Japanese Patent Unexamined Publication No. SHO 64-46011), a method including the steps of dipping the assembled rolling bearing 700 in a lubricant, picking up the rolling bearing 700 from the lubricant and removing the lubricant therefrom in a centrifugal fashion (Japanese Patent Unexamined Publication No. HEI 8-303467), or a method including the steps of dipping the rolling bearing 700 in a lubricant diluted with a solvent (petroleum benzine) and thereafter allowing the solvent to evaporate (Japanese Patent Unexamined Publication No. HEI 5-149343).
Widely adopted as a means for assembling the rolling bearing 700 to an apparatus is a method for adhering a radially inner surface of the inner race 702 to a shaft or for adhering a radially outer surface of the outer race 701 to a housing. In these methods, the adhering surfaces of the rolling bearing 700 are required to be dry (hereinafter, described as a first case).
In addition, in an apparatus such as a hard disk drive in which a high degree of cleanness is required in the interior thereof, The volume of lubricant component running out of or flying from the rolling bearing 700 needs to be as little as possible. This requires a flat portion as well as the radially inner and outer surface portions of the rolling bearing 700 to be sufficiently dry. Moreover, if there is some lubricant adhering to a sealing groove portion formed in the outer race 701 and the inner race 702, this adhering lubricant runs out of the sealing groove portion when a seal is inserted thereinto, and therefore this sealing groove portion also needs to be sufficiently dry (hereinafter, described as a second case).
Furthermore, a fiber constituent contained in grease as a lubricant is not too good to reduce and stabilize the torque of the rolling bearing, and therefore there are some rolling bearings 700 in which grease is required to be put on the retainer 704 in order to reduce and stabilize the torque thereof. In this case, when some of the lubricant required for lubrication in an initial stage (oil component in the grease runs out thereof soon after the initial stage and this oil component contributes to the lubrication of the rolling bearing) adheres to the portion where grease is put, the grease becomes easy to slide down over the retainer 704, and it moves and comes to adhere to rolling element raceway surfaces of the outer and inner races 701, 702 while the rolling bearing 700 is rotating. Therefore, the torque is increased and caused to vary. In order to prevent this, no lubricant has to adhere to the portion of the retainer 704 where grease is put (hereinafter, described as a third case).
In addition, there is a case where any combination out of the above three cases simultaneously constitutes a problem. In other words, a problem is caused by a combination of the first and second cases, the first and third cases, or the second and third cases. Moreover, there is a case where the first, second and third cases simultaneously constitute a problem.
Namely, it is important that no lubricant adheres to any portion in the interior of the rolling bearing 700 that does not really needs lubrication. What needs lubrication in the interior of the rolling bearing 700 are the rolling element raceway surfaces of the outer and inner races 701, 702 and the surface of the rolling elements 703.
In the aforesaid conventional example, however, it is not possible to apply a lubricant only to portions in the interior of the rolling bearing 700 which need lubrication and it is unavoidable that a relatively large volume of oil component adheres to portions in the interior of the rolling bearing 700 other than those that really need lubrication. In addition, in the above-described conventional example, it is very difficult to dry only the exterior of the rolling bearing 700 with a needed volume of lubricant being left in the interior thereof. Moreover, manual removal of oil component adhering to the exterior of the rolling bearing 700 causes an increase in costs.
Moreover, it becomes important to inspect whether or not a lubricant is injected into the interior of a rolling bearing through a total inspection for judgement of defective or non-defective. However, in the methods described in the aforesaid publications, only the process of applying the lubricant is described and none of the methods describes therein a process of inspecting a lubricant applied condition of the rolling bearing after the lubricant is applied thereto. Thus, there is caused a problem that whether or not the lubricant is properly applied to the completed rolling bearing is unclear.
The present invention was made in view of the aforesaid problems inherent in the related art, and an object thereof is to provide a system for easily and securely applying a lubricant only to portions in the interior of a rolling bearing which really need lubrication and further for inspecting the lubricant applied condition of the rolling bearing by optical detection.
With a view to attaining the above object, according to a first aspect of the present invention, there is provided a method for applying a lubricant to a rolling bearing by using a prescribed liquid volume discharge device comprising at least one discharge port, the method including the steps of placing the discharge port directly above and sufficiently close to a rolling element of the rolling bearing, and transferring a prescribed volume of the lubricant from the discharge port to the rolling element for application of the lubricant to the interior of the rolling bearing.
Further, according to a second aspect of the present invention, there is provided a method and apparatus for inspecting a lubricant applied condition of a rolling bearing adapted to inspect whether or not a prescribed volume of lubricant is discharged from a lubricant discharge device for injecting a lubricant in the interior of a rolling bearing. A laser beam is irradiated between a discharge port of the lubricant discharge device and the rolling bearing, and a reflected laser beam reflected by a lubricant when the lubricant is discharged from the discharge port is received by a photoreceptor device disposed on an optical axis of the reflected laser beam, whereby whether or not the lubricant is applied to the rolling bearing is inspected based on an output from the photoreceptor device.
In the method and apparatus for inspecting a lubricant applied condition of a rolling bearing, when the lubricant is injected into the interior of the rolling bearing from the discharge port of the lubricant discharge device, for instance, while a ball of the rolling bearing is caused to approach to a distal end of the discharge port and then the lubricant is discharged, the laser beam is irradiated between the discharge port and the rolling bearing, and the reflected laser beam reflected by the lubricant is received by the photoreceptor device. Since the photoreceptor device is disposed on the optical axis of the reflected laser beam, in a case where a prescribed volume of the lubricant is not discharged, the reflected laser beam is reflected in a different direction or there is reflected no laser beam, whereby the photoreceptor device receives no light. Thus, the output varies depending on whether or not there is reflected a laser beam, and therefore whether or not the prescribed volume of lubricant is discharged can be judged based on the output from the photoreceptor device, whereby the lubricant applied condition of the rolling bearing can be inspected.
Raised as a specific inspection device for carrying out the above method for inspecting a lubricant applied condition of a rolling bearing according to the present invention is an inspection device for inspecting a lubricant applied condition of a rolling bearing which comprises a discharge device for injecting a prescribed volume of lubricant into the interior of the rolling bearing, a laser beam projector for irradiating a laser beam between a discharge port of the discharge device and the rolling bearing, and a photoreceptor disposed on an optical axis of a reflected laser beam produced when the laser beam from the laser beam projector is reflected by the lubricant for receiving the reflected laser beam, whereby whether or not the lubricant is applied to the rolling bearing is inspected based on an output from the laser beam receptor.
In this device for inspecting a lubricant applied condition of a rolling bearing, when the prescribed volume of lubricant is injected into the interior of the rolling bearing by the discharge device, the laser beam is irradiated between the discharge port of the discharge device and the rolling bearing by the laser beam projector, and the reflected laser beam produced when the laser beam from the laser beam projector is reflected by the lubricant is then received by the laser beam receptor. In other words, in a case where the prescribed volume of lubricant is discharged, the reflected laser beam from the lubricant is detected, while in a case where the prescribed volume of lubricant is not discharged, the reflected laser beam is oriented in a different direction, there being no reflected laser beam that can be detected by the photoreceptor.
In addition, since the reflected laser beam enters the laser beam photoreceptor only when the lubricant is discharged from the discharge device, after the completion of discharge there is no reflected laser beam that can detected by the laser beam photoreceptor. Thus, the output of the laser beam photoreceptor only exhibits a large momentary variation in level thereof. Since a momentary variation in output level like that has to be detected with high sensitivity, it is desirable to interpose a peak hold circuit to thereby securely detect the output of the photoreceptor that is to vary when the reflected laser beam is received by the photoreceptor.
Furthermore, the discharge of the lubricant from the discharge device into the interior of the rolling bearing and inspection of a lubricant applied condition may be carried out sequentially for individual balls or at one time for the respective balls. In a case where the discharge or inspection is carried out at one time for the respective balls, a representative inspection of a lubricant applied condition may be carried out only for one ball, this helping simplify the inspection.
Although the laser beam projector and laser beam photoreceptor may be disposed separately in order to increase the degree of freedom of design, they may be integrated into one construction in order to simplify operations of assembling and regulating of the inspection device.
Furthermore, the following are raised as other methods and apparatus for inspecting a lubricant applied condition of a rolling bearing.
Namely, there are provided a method and apparatus for inspecting a lubricant applied condition of a rolling bearing adapted to inspect whether or not a prescribed volume of lubricant is discharged from a lubricant discharge device for injecting a lubricant into the interior of the rolling bearing, wherein a substance is added to the lubricant which emits fluorescence when excited with an ultraviolet ray, wherein an ultraviolet ray is irradiated to the rolling bearing while cutting off external light, wherein an image of the rolling bearing to which the ultraviolet ray is so irradiated is picked up and wherein a lubricant applied condition is inspected based on the existence of fluorescence reflected in the picked-up image.
In this method and apparatus for inspecting a lubricant applied condition of a roller bearing, since the lubricant applied surface emits fluorescence when the prescribed volume of lubricant is discharged and applied to the rolling bearing, it is possible to quickly inspect the lubricant applied condition of the rolling bearing by detecting the fluorescence so emitted.
As an additive emitting the aforesaid fluorescence, for instance, an antioxidant of amine system may be used which does not damage the lubricating properties of the lubricant used.
Provided as a specific inspection device for carrying out the above method for inspecting a lubricant applied condition of a rolling bearing according to the present invention is an inspection device for inspecting a lubricant applied condition of a rolling bearing which is adapted to inspect whether or not a prescribed volume of lubricant having added therein a substance adapted to emit fluorescence when excited with an ultraviolet ray is discharged from a lubricant discharge device for injecting the lubricant into the interior of the rolling bearing and comprises a light cut-off hood for cutting off external light so that the rolling bearing to be inspected is not exposed to the external light, a black light provided inside the light cut-off hood for irradiating an ultraviolet ray to the rolling bearing and a video camera for picking up an image of the rolling bearing irradiated with the ultraviolet ray by the black light, whereby the lubricant applied condition is inspected based on the existence of fluorescence reflected in the image picked up by the video camera.
In this inspecting device, in a case where the prescribed volume of lubricant is applied to the rolling bearing, the fluorescence is reflected over a predetermined area in the picked up image when an image of the rolling bearing irradiated with the ultraviolet ray by the black light is picked up by the video camera, while in a case where the prescribed volume of the lubricant is not applied to the rolling bearing, an area reflecting the fluorescence is less than the predetermined area, or there is no fluorescence reflected in the picked up image. Thus, whether or not the prescribed volume of the lubricant is discharged from the lubricant discharge device is inspected based on the fluorescence reflecting area.